Optimization of logical rings for multi-hop transmissions in WDM optical star networks
ABSTRACT In this paper, we present a multi-hop scheduling algorithm for the All-to-All Broadcast (AAB) problem in Wavelength Division Multiplexed (WDM) optical star networks with N nodes. To decrease the packet delay in packet transmissions, our scheduling algorithm will limit the hop distance to a constant ρ. We transfer the ρ-hop AAB problem to the Hamiltonian cycles problem and then generate the logical rings for physical packet transmissions. In order to minimize the scheduling length, the problem of selection of logical rings is to minimize the number of tuning operations to reduce the influence of tuning latency δ for the AAB problem. We propose a 2-approximation algorithm that needs only 2⌈(N − 1)/ ρ⌉ tuning operations in an AAB scheduling. When , the schedule length of our algorithm will be shorter than that of the optimal single-hop scheduling algorithm.
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ABSTRACT: A linear time algorithm to obtain a minimum finish time schedule for the two-processor open shop together with a polynomial time algorithm to obtain a minimum finish time preemptive schedule for open shops with more than two processors are obtained. It is also shown that the problem of obtaining minimum finish time nonpreemptive schedules when the open shop has more than two processors is NP-complete.J. ACM. 01/1976; 23:665-679.
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ABSTRACT: This paper presents a scalable optimal logical topology scale-net for multi-hop optical networks based on de Bruijn graph, a regular non-scalable one with simple routing strategy. In addition to its scalability property, this new topology maintains the simplicity in routing as in de Bruijn graph while keeping its diameter same throughout the insertion of nodes as that in a de Bruijn graph where the diameter is of logarithmic value of its number of nodes. Also, perturbation in the network is maintained at a very low level, while inserting a node in the network. Simulation results also show a reasonable average hop distance between any source destination pair of the topology developed.Computer Communications. 01/2005; 28:557-570.
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ABSTRACT: We consider the problem of scheduling packet transmissions in a broadcast, single-hop wavelength-division multiplexing (WDM) network, with tunability provided only at one end. Our objective is to design schedules of minimum length to satisfy a set of traffic requirements given in the form of a demand matrix. We address a fairly general version of the problem as we allow arbitrary traffic demands and arbitrary transmitter tuning latencies. The contribution of our work is twofold, First we define a special class of schedules which permit an intuitive formulation of the scheduling problem. Based on this formulation we present algorithms which construct schedules of length equal to the lower bound provided that the traffic requirements satisfy certain optimality conditions. We also develop heuristics which, in the general case, give schedules of length equal or very close to the lower bound. Secondly, we identify two distinct regions of network operation. The first region is such that the schedule length is determined by the tuning requirements of transmitters; when the network operates within the second region however, the length of the schedule is determined by the traffic demands, not the tuning latency. The point at which the network switches between the two regions is identified in terms of system parameters such as the number of nodes and channels and the tuning latency. Accordingly, we show that it is possible to appropriately dimension the network to minimize the effects of even large values of the tuning latencyIEEE/ACM Transactions on Networking 07/1997; · 2.01 Impact Factor